// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

namespace Microsoft.CodeAnalysis;

public partial class ProjectDependencyGraph
{
    internal ProjectDependencyGraph WithAdditionalProject(ProjectId projectId)
    {
        // Track the existence of some new projects. Note this call only adds new ProjectIds, but doesn't add any references. Any caller who wants to add a new project
        // with references will first call this, and then call WithAdditionalProjectReferences to add references as well.

        // Since we're adding a new project here, there aren't any references to it or from it (any references will be added
        // later with WithAdditionalProjectReferences). Thus, the new projects aren't topologically sorted relative to any other project
        // and form their own dependency set. Thus, sticking them at the end is fine.
        var newTopologicallySortedProjects = _lazyTopologicallySortedProjects;

        if (!newTopologicallySortedProjects.IsDefault)
        {
            newTopologicallySortedProjects = newTopologicallySortedProjects.Add(projectId);
        }

        var newDependencySets = _lazyDependencySets;

        if (!newDependencySets.IsDefault)
        {
            var builder = newDependencySets.ToBuilder();
            builder.Add([projectId]);
            newDependencySets = builder.ToImmutable();
        }

        // The rest of the references map is unchanged, since no new references are added in this call.
        return new ProjectDependencyGraph(
            ProjectIds.Add(projectId),
            referencesMap: _referencesMap,
            reverseReferencesMap: _lazyReverseReferencesMap,
            transitiveReferencesMap: _transitiveReferencesMap,
            reverseTransitiveReferencesMap: _reverseTransitiveReferencesMap,
            topologicallySortedProjects: newTopologicallySortedProjects,
            dependencySets: newDependencySets);
    }
}